Certain weeds such as Ipomoea, Cyperus, Sida and Euphorbia are particularly difficult to control. Their full-season competition can reduce crop yields and cause significant economic loss in row-crop production. One of the most common practices for controlling these troublesome weeds is the postemergent application of a herbicide. However, there is no single selective herbicide currently available which will give economic control of these weeds.
Glyphosate [(N-phosphonomethyl)glycine] is a highly effective herbicide with a broad spectrum of activity. However, certain agronomically important weed species require relatively high application rates of glyphosate for effective control. High rates of glyphosate can lead to undesirable increased selection pressure. Glyphosate tolerance, particularly in Ipomoea, is a recognized problem in the field. Therefore, new weed control methods and compositions which effectively lower glyphosate application rates while providing broad spectrum weed control are highly desirable.